During install antivir (avira free antivirus) says there is a troyan TR/ATRAPS.Gen in file is-c7663,tmp and gogstart.exe.

Has someone experienced an alert like that?

Yes I saw no one reported such an alert and no other gog game I bought gives me this thrill:-)

There have been a few other instances of false positives with other games, most likely that's what you have there, but you can always scan your PC with Malwarebytes if you want extra reassurance.

Hey guys, just wanted to let you know that my Avira is reporting this is well.
I'm considering it a false positive since I highly doubt that GOG would include viruses in their games!

Still, somebody ought to fix this. In my AntiVirus ends up shutting down the game every time it sees that file, I'm gonna be angry.

EDIT: I've just submitted the file to Avira as a false positive. They're currently analyzing it. Will report back if they have anything to say.

EDIT McEDIT: That was quick:
"The file 'gogstart.exe' has been determined to be 'FALSE POSITIVE'. In particular this means that this file is not malicious but a false alarm. Detection will be removed from our virus definition file (VDF) with one of the next updates."

We should be over this problem when they update their definitions